Use on-disk compilation unit if available

If we succeeded in saving the compilation unit to disk, then attempt to use it
right away. This replaces the C++ heap usage for the compilation unit data as
well as the anonymous allocated executable memory with file-backed mmap'ed
memory. That means the memory can be discarded when overall availability is low
and paged in on-demand.

Change-Id: Ide1b1e11752d861eb049a99a26ca12cec5e2502e
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/qml/compiler/qv4compileddata_p.h b/src/qml/compiler/qv4compileddata_p.h
index d6537bbab3..639c79f79b 100644
--- a/src/qml/compiler/qv4compileddata_p.h
+++ b/src/qml/compiler/qv4compileddata_p.h
@@ -666,8 +666,10 @@ struct Unit
             return QString();
 #if Q_BYTE_ORDER == Q_LITTLE_ENDIAN
         const QChar *characters = reinterpret_cast<const QChar *>(str + 1);
-        if (flags & StaticData)
-            return QString::fromRawData(characters, str->size);
+        // Too risky to do this while we unmap disk backed compilation but keep pointers to string
+        // data in the identifier tables.
+        //        if (flags & StaticData)
+        //            return QString::fromRawData(characters, str->size);
         return QString(characters, str->size);
 #else
         const LEUInt16 *characters = reinterpret_cast<const LEUInt16 *>(str + 1);